Based on observed damage patterns from previous earthquakes and a rich history of analytical studies,
asynchronous input motion has been identified as a major source of unfavorable response for long span
structures, such as bridges. This study is aimed at quantifying the effect of geometric incoherence and
wave arrival delay on complex straight and curved bridges using state-of-the-art methodologies and tools.
Using fully parameterized computer codes combining expert geotechnical and earthquake structural
engineering knowledge, suites of asynchronous accelerograms are produced for use in inelastic dynamic
analysis of the bridge model. Two multi-degree-of-freedom (MDOF) analytical models are analyzed
using 2,000 unique synthetic accelerograms. Results from this study indicate that response for the 344
meter study structure is amplified significantly by non-synchronous excitation, with displacement
amplification factors between 1.6 and 3.4 for all levels of incoherence. This amplification was not
constant or easily predicable, demonstrating the importance of inelastic dynamic analysis using
asynchronous motion for assessment and design of this class of structure. Additionally, deck stiffness is
shown to significantly affect response amplification, through response comparison between the curved
and an equivalent straight bridge. Study results are used to suggest an appropriate domain for
consideration of asynchronous excitation as well as an efficient methodology for analysis.